Shield for transformers



Oct. 12, 1948. c. H. DUNTON 2,451,324

SHIELD FOR TRANSFORMERS Filed Oct. 16, 1945 Patented Oct. 12, 1948 UNITED STATES PATENT OFFICE SHIELD FOR TRANSFORMERS Charles H. Dunton, Oakland, Calif.

Application Qctober 16, 1945, Serial No. 622,508

4. Claims.

1 This invention, a transformer, is a modification of the transformer disclosed in my United States Patent No. 2,388,473, and ofifering certain improvements with consequent advantages thereover, in that certain flux leakage is overcome resulting in increased power factor and ef- Similar to that disclosed in the previous application, this transformer has its secondary shielded from the primary by a conductive shield, the original transformer having a single conductive shield formed of a series of rings and with the rings insulated from each other, thus dividing the shield into a multiplicit of sections, and without any air-gap, while this improved transformer has a double shield one within the other and with adjacent terminals separated to form an air-gap and with the two conductively connected at the terminals, so that a current flows in one shield in one direction thence back in the opposite direction through the other shield to form a complete circuit, which due to the flow of current in opposite directions in the two shields neutralizes any flow of magnetic flux direct be-- tween primary and secondary.

Unlike the. original transformer mentioned above, which has a shield which completely shields the secondary, this transformer has a complete double shield with the exception of the space occupied by the air-gap which is located at a most remote point from the primaries.

In the previous transformer it was found that there was some leakage of flux between the rings forming the shield, and this has been completely overcome by the complete circuit arrangement of the coaxial sleeves with air-gap, resulting in marked efliciency.

The objects and advantages of the invention are as follows:

First, to provide a transformer with a new and unusual type of flux-isolating shield between primary and secondary.

Second, to provide a transformer of increased efficiency, and a power factor as close to unity as possible.

Third, to provide a transformer with a conductive shield between the primary and secondary and which consists of two coaxial sleeves one Within the other and enclosing the secondary with the exception of terminal portions separated to form an air-gap, and with the respective sleeves functioning as conductors for carrying current in opposite directions to form a complete circuit.

Fourth, to provide a shield for the secondary of a transformer consisting of an inner shield and an outer shield conductively connected at terminal ends and with an air-gap between the terminal ends and with the shield longitudinally divided for assembly at will about the pre-wound secondary.

Fifth, to provide circulatin paths throughout all parts of the transformer for cooling fluids.

In describing the invention reference will be made to the accompanying drawings in which:

Fig. 1 is a top plan view of my new transformer with a small section broken away to disclose the secondary winding within the shield.

Fig. 2 is an enlarged cross-section taken on line 22 of Fig. 1.

Fig. 3 is a vertical section through the shield illustrated in Fig. 2.

Fig. 4 illustrates a rectangular type of shield.

Fig. 5 is a modification in which the shield is circular in cross-section.

The. invention consists of a shield 20 for the secondary of a power transformer which completely stops the flow of flux direct between the primary and secondary. It consists of two sleeves, H and I2 which completely enclose the secondary l3 throughout its circular extent with the exception of the space It bet-ween the terminal ends 15 and I 6 which space provides an air-gap or break in the circuit of the shield. Suitable spacers ll of insulation are provided for the gap and the bolts l8 are suitably insulated from the shield as indicated at IS.

The shield is divided as indicated at 20 and 2| to facilitate manufacture and for rapid and easy assembly about the secondary, the two halves being bolted together at assembly as indicated at 22.

The inner and outer shields are conductively connected at the terminal ends l5 and 16 as indicated at 23 and suitable spacers 24 maintain suitable spacing between the two sleeves.

As illustrated in Fig. 1, the shield may be continuous from terminal to terminal and with round ends, or may be made up in sections as illustrated in Fig. 4, in which the respective sections are secured together such as by bolting indicated at 25, all sections being conductively connected except at the gap M.

The shield may have any suitable cross-sectional form, being illustrated as square in Fig. 2 and circular in Fig. 5.

A suitable inlet 26 and outlet 2! for the cooling fluid are provided adjacent to the respective terminals of the shield and provide for circulation between the secondary and the inner shield and between the inner and outer shields for thorough absorption of heat,

The magnetizable cores 28 are preferably formed of interlapping laminations as indicated at 29 and 30 for convenience in assembly of the transformer.

The secondary is form-wound to fit within the shield. The secondary is then laid in one half of the shield and the other half is then placed on top with the secondary terminals 31 and 32 brought out through the insulating bushings 33 and 34. The two halves are then bolted together as indicated at 22, the insulating spacers I! are placed between the terminal ends and these terminal ends are then bolted in position with suitable insulation between the bolts and shield, so that no current can flow in a complete circuit throughout the shield.

The primaries are also form-wound, the core laminations being assembled about the shield and within the primary windings.

Thus, a double shield is provided between the primary and secondary windings with current flowing in opposite directions in the respective members of the shield and efiectively blocking the flow of flux direct between the primar and secondary.

I claim:

1. A shield for the secondary of a transformer consisting of two coaxial conductive members one within the other and having spaced walls and terminal ends with the secondary winding of the transformer enclosed in the inner of the two members, and with the two members conductively connected only at each terminal end to form a complete circuit through one member, across the connection at one terminal end, back through the other member, and across the connection at the other terminal end.

2. A shield consisting of an inner shield and an outer shield enclosing the inner shield and each having terminal ends, and with the walls of the shields between the terminal ends spaced, and the terminal ends conductively connected to provide a complete circuit between the two shields for fiow of current, with the current fiowable in opposite directions in the respective shields.

3. A shield for a transformer consisting of an inner sleeve and an outer sleeve enclosing the inner sleeve and each having terminal ends, and with the walls of the sleeves spaced apart except at said terminal ends and conductively connected at the terminal ends only to provide a complete circuit through the two sleeves for flow of current, with the current flowable in opposite directions in the respective sleeves; each of said sleeves being formed in two connectable sections with the parting lines of the respective sleeves staggered relative to and parallel with the planar axis of the shield for convenience in applying the shield over the secondary winding of a transformer.

4. A shield for the secondary of a transformer comprising; a hollow body of conductive material for enclosing the secondary and extending substantially throughout the circuitous length of the secondary and having terminal ends insulated from each other to interrupt completion of a circuit through the walls of the hollow body, and a second conductive hollow body enclosing said hollow body and insulated therefrom and having its walls spaced from the walls of said hollow body, and having terminal ends in common with the terminal ends of said hollow body and conductively connected thereto, to form a complete circuit through the hollow body and second conductive hollow body, with the current flowing in opposite directions in said hollow body and said second hollow body.

CHARLES H. DUNTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 792,248 Campbell June 13, 1905 1,326,005 Steinmetz Dec. 23, 1919 1,561,204 Beers Nov. 10, 1925 1,899,981 Oesterreicher Mar. 7, 1933 2,161,192 Peterson June 6, 1939 2,241,914 Koschmieder May 13, 1941 2,280,625 Camilli Apr. 21, 1942 2,388,473 Dunton Nov. 6, 1945 

